Yeah, I have to question the consistancy of the quality control on these transmissions... Some folks are lucky, other's aren't. My original transmission had a bearing failure. I bought a used replacement '02 trans it lost 2 teeth off of second gear literally coasting into my driveway at <5mph, and 2nd gear still worked! But who knows how the previous owner treated it, probably was just a time bomb waiting to go off anyway, better in my driveway than having to get it towed from somewhere far away.
I think a lot of times there are small cracks that develop in the case hardened surface of the gear teeth during hard driving that then finally give up later on down the road, sometimes just cruising around.